Komodo Airdrop

This Airdrop crate makes it easy to perform an airdrop from a Komodo Platform Assetchain, using KMD or any other assetchain.

```rust extern crate komodo_airdrop;

fn main() {
let snapshot = komodoairdrop::Snapshot::builder() .onchain(Chain::CHAIN) .excludeaddresses(vec![ String::from("REbwjC5mfQBRevH78CuRjcvQudxa3ii5Ma"), String::from("RU9F2EdDzUNK4LUMgjLTMDmtCmDK1a9vrY"), String::from("RYEufBcEUsofxwt4bGUdroRGmAQxBR8aJG") ]) .usingthreshold(1.0) // only include addresses that contain at least 1 CHAIN .build() .unwrap();

let airdrop = komodo_airdrop::Airdrop::builder()
    .using_chain(Chain::KMD)
    .include_interest(true)
    .using_snapshot(&snapshot)
    .fund_address("RQT7m4jcnWQxwqQQzh77WKNCuZotkRkAuk")
    .payout_ratio(0.75)
    .build()
    .unwrap();

} ```

If an airdrop happens from a multisig address (starts with b):

```rust let signingstring = airdrop.signingstring(Some(String::from(""))); println!("{}", signing_string);

```

If not:

rust let signing_string = airdrop.signing_string(None); println!("{}", signing_string);

signing_string creates a raw transaction from the inputs of all utxos in the fund_address, and uses the resulting hex (a running daemon of the fund_address blockchain is required) to create a string that can be used as parameter string for the signrawtransaction daemon RPC, where in case of a multisig, a private key (WIF) needs to be supplied manually by the signer.

notes:

ratio is applied to both balance and interest. any change includes interest against the same ratio

todo:

[ ] documentation
- [x] why this airdrop crate is needed: KMD platform addresses are the same etc, so the only differentiator is an AC
[x] define static payout amount in addition to ratio
[x] ~~let the builder pattern work with Results (trait type?)~~ impossible, checking is done in build() now
[x] send back any remainders and/or interest to fund_address
[x] add P2SH inputs to support multisig airdrop
[x] airdrop take a reference to snapshot
[ ] use JSON file as input to Airdrop
[ ] only include necessary utxos as input to the transaction, to prevent using all utxos when it's not needed since the required amount to airdrop has been reached.
- [ ] what about interest? if KMD && interest_included then spend all inputs to include all interest.
- [ ] else spend only required utxos
  - with some kind of ordering of utxos to only use largest utxos
[ ] use a global komodod daemon client instead of instantiating it a couple of times.
[ ] use an Enum for ratio and amount in Airdrop
[ ] Enum: add nonexhaustive to not have a breaking change when adding a new Enum variant

scenarios tested

[ ] Multisig yes/no
[ ] Ratio
[ ] Amount
- payout full amount
[ ] Interest included

long term maybe's:

[ ] serialize multisig raw tx for easy multiparty signing
- would likely be separate crate